How It Works

Anticoagulants are often called blood
thinners, but they don't really thin blood. They work by increasing the time it
takes for a blood clot to form. This prevents an existing clot from increasing
in size, thereby preventing a
heart attack or
stroke.

Why It Is Used

Anticoagulants are not typically used to treat coronary artery disease. But you might take them after having angioplasty or bypass surgery. You might take an anticoagulant if you also have atrial fibrillation or other complications.

How Well It Works

Anticoagulants lower the risk of problems caused by blood clots, such as stroke.footnote 1

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

Usually the benefits of the medicine are more important than any minor side effects.

Side effects may go away after you take the medicine for a while.

If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Allergic reaction

Call 911 or other emergency services right away if you have:

Trouble breathing.

Swelling of your face, lips, tongue, or throat.

Call your doctor if you have:

Hives.

Bleeding

Call 911 or other emergency services right away if you have:

A sudden, severe headache that is different from past headaches. (It may be a sign of bleeding in the brain.)

Call your doctor now or seek
immediate medical care if you have:

Any abnormal bleeding, such as:

Nosebleeds.

Vaginal bleeding that is different (heavier, more frequent, at a different time of the month) than what you are used to.

Bloody or black stools, or rectal bleeding.

Bloody or pink urine.

If you are injured, apply pressure to stop the bleeding. Realize that it
will take longer than you are used to for the bleeding to stop. If you can't get the bleeding to stop, call your doctor.

Heparin: Side effects often happen at injection sites. These side effects include:

Pain.

Irritation.

Bruising.

Warfarin: Other side effects include:

Skin rash.

See Drug Reference for a full list of side effects. (Drug Reference is
not available in all systems.)

What To Think About

When you take anticoagulants, you need to take extra steps to avoid bleeding problems.

Long-term use of heparin is not typically
recommended. It requires one or two injections each day. And long-term use is linked with
osteoporosis.

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women

Warfarin

Do not take warfarin if you are pregnant. Warfarin can cause miscarriage or birth defects. If you are taking warfarin, talk to your doctor about how you can prevent pregnancy.

If you think you might be pregnant: Call your doctor. If you are pregnant, you will take heparin during your pregnancy.

If you plan on getting pregnant: Talk with your doctor. You and your doctor will decide which medicine you will take—warfarin or heparin—while trying to get pregnant.

Heparin

If you are pregnant: You will take heparin during your pregnancy. Heparin has not been shown to affect the fetus.

Checkups

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

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